Answer: In my experience, weeds will seed themselves down in between the rock, so this will not really solve a weed problem. In addition, any uneven spaces in the plastic can trap water and become a breeding place for mosquitoes. Also, you need to maintain a slight slope leaning away from the foundation to allow water to run off rather than collect against the house. Finally, the plastic makes an unhealthy environment for the roots of any foundation plants you wish to keep.
If weeds are a problem you could try killing them with an herbicide containing glyphosate, then put down a weed barrier fabric that is permeable to both water and air. Lay the stone on top of the fabric. (This prevents it from frost heaving and working its way down into the soil.) Then use a pre-emergent weed preventer such as corn gluten to prevent weed seeds from germinating. Read and carefully follow all of the label directions for best results.
Also, plan on raking or using a blower to clean off the stone periodically to remove any fallen leaves or debris. You may also need to weed perodically to remove any weeds that do manage to grow there despite your best efforts.
Leave a bare strip of ground along the edge of the rock to separate it from the lawn. When you mow, run the mower wheels on that bare strip and be sure you are directing the clippings outward away from the stones. These eliminates the need for weed whacking and should prevent clippings from landing in the stone. If they do, allow them to dry for a day or two and then sweep or blow them off.
Good luck with your project!
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